4 x 4 Australia - - Tech Torque -

THE as­ton­ish­ing im­prove­ment in diesel per­for­mance, econ­omy and re­fine­ment over the last 15 years has come largely from ad­vances in elec­tron­i­cally con­trolled high-pres­sure com­mon-rail fuel in­jec­tion and tur­bocharger tech­nol­ogy.

High fuel pres­sure means fuel is in­jected into the com­bus­tion cham­ber in dis­tinct ‘squirts’ for each com­bus­tion event, al­low­ing com­bus­tion to be op­ti­mised for per­for­mance or econ­omy – or any­where in be­tween – de­pend­ing on the de­mand. The com­mon­rail’s part­ner is the fast-switch­ing piezo-crys­tal in­jec­tor that has largely re­placed the slower elec­tro­mag­netic so­le­noid in­jec­tor.

Tur­bocharg­ers ben­e­fit most from vari­able vane ge­om­e­try, which helps the trade-off be­tween turbo re­sponse and pump­ing ca­pac­ity. Se­quen­tial tur­bos, where small and large tur­bos work to­gether, do an ever bet­ter job of ad­dress­ing these two con­flict­ing de­mands.

Plus, diesel com­pres­sion ra­tios have dropped from about 22:1 to around 16:1 for re­fine­ment, qui­eter op­er­a­tion, less knock, and lower NOX emis­sions.

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